Display control apparatus used for color matching between reference image pickup apparatus and adjustment image pickup apparatus, control method therefor, and storage medium storing control program therefor

ABSTRACT

A display control apparatus that easily discriminates residual color difference between a plurality of image pickup apparatuses at a site where the image pickup apparatuses are used. The display control apparatus including a memory device that stores a set of instructions, and at least one processor that executes the set of instructions to obtain an adjustment image from an adjustment image pickup apparatus that performs predetermined color matching with a reference image pickup apparatus, generate residual color difference information showing color difference from a reference image picked up by the reference image pickup apparatus that remains in the adjustment image, and generate display information from the residual color difference information.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a display control apparatus used forcolor matching between a reference image pickup apparatus and anadjustment image pickup apparatus, a control method therefor, and astorage medium storing a control program therefor.

Description of the Related Art

Japanese Laid-Open Patent Publication (Kokai) No. 2018-088618 (JP2018-088618A) discloses an image pickup apparatus. This image pickupapparatus allocates a pixel value of a saturation-pixel warning color toa saturation pixel in an image picked up by an image pickup system.Moreover, the image pickup apparatus allocates a pixel value, which isobtained by converting an imaging color gamut into a display colorgamut, to a pixel within the display color gamut in the image picked upby the image pickup system. Furthermore, the image pickup apparatusallocates a pixel value of an out-of-display-color-gamut warning colorto a pixel without the display color gamut in the image picked up by theimage pickup system.

Japanese Laid-Open Patent Publication (Kokai) No. 2003-224775 (JP2003-224775A) discloses a technique that enables a user to easilyvisually recognize a part changed in time series of an object by addinga difference image between a plurality of images picked up in timeseries to an image that is obtained by lowering contrast of thedifference image.

Incidentally, such an image pickup apparatus picks up a static image ora video image by receiving light entering through an optical systemusing an image sensor like a CCD sensor or a CMOS sensor, for example.Then, an image pickup apparatus may be used with another image pickupapparatus. In this case, even if a plurality of image pickup apparatusespick up the same object, colors of the object in images may be differentbecause of difference in light receiving characteristic between theimage sensors of the image pickup apparatuses. Hereinafter, differencebetween colors in images picked up by image pickup apparatuses is calledcolor difference.

In order to correct the color difference, it is considerable to use oneimage pickup apparatus as a reference image pickup apparatus, to useanother image pickup apparatus as an adjustment image pickup apparatus,and to generate a correction lookup table used by the adjustment imagepickup apparatus so as to match colors. This should be able to match thecolors of the image of the adjustment image pickup apparatus with thatof the reference image pickup apparatus.

However, even if the adjustment image pickup apparatus uses such acorrection lookup table, not all the colors of the pickup image of theadjustment image pickup apparatus match the colors of the pickup imageof the reference image pickup apparatus. On a site where a plurality ofimage pickup apparatuses are used actually, the color difference mayremain in some objects even if the correction lookup table is used.Hereinafter, the color difference that remains after correction usingthe correction lookup table is called residual color difference. Whenthere is such residual color difference, a user needs much effort tofind the residual color difference by visually comparing the pickupimage of the reference image pickup apparatus and the pickup image ofadjustment image pickup apparatus.

SUMMARY OF THE INVENTION

The present invention provides a technique that easily discriminates theresidual color difference between a plurality of image pickupapparatuses at a site where the image pickup apparatuses are used.

Accordingly, an aspect of the present invention provides a displaycontrol apparatus including a memory device that stores a set ofinstructions, and at least one processor that executes the set ofinstructions to obtain an adjustment image from an adjustment imagepickup apparatus that performs predetermined color matching with areference image pickup apparatus, generate residual color differenceinformation showing color difference from a reference image picked up bythe reference image pickup apparatus that remains in the adjustmentimage, and generate display information from the residual colordifference information.

The present invention enables easy discrimination of the residual colordifference between the reference image pickup apparatus and theadjustment image pickup apparatus at the site where these image pickupapparatuses are used.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram showing a color difference correctionsystem that corrects color difference between a plurality of imagepickup apparatuses and includes a display control apparatus according toa first embodiment of the present invention.

FIG. 2 is a block diagram showing a main configuration of the displaycontrol apparatus in FIG. 1 .

FIG. 3 is a flowchart showing a process for generating a correction LUT(lookup table) by the display control apparatus in FIG. 1 .

FIG. 4 is a view showing an example of a combination of a pickup imageof a reference camera and a pickup image of a target camera that arecurrently displayed on a display unit of the display control apparatus.

FIG. 5 is a view showing an example of a combination of RGB values ofcolor patches in the pickup images in FIG. 4 .

FIG. 6 is a view showing an example of a combination of XYZ values ofthe color patches obtained on the basis of the RGB values of the colorpatches in FIG. 5 .

FIG. 7 is an explanatory view of an example of the correction LUTgenerated by the display control apparatus in FIG. 1 .

FIG. 8 is a flowchart showing a process for generating residual colordifference information about the target camera that uses the correctionLUT.

FIG. 9 is a view showing an example of a combination of RGB values ofcolor patches in an image from the target camera to which color matchinghas been applied.

FIG. 10 is a view showing an example of a combination of XYZ valuesafter the color matching that are obtained on the basis of the RGBvalues of the color patches in FIG. 9 .

FIG. 11 is a flowchart showing a process for generating a display imagefor displaying the residual color difference information.

FIG. 12 is a table showing correspondence relations between ranges of aresidual color difference value defined by the residual color differenceinformation and conversion colors used as colors of pixels included inthe respective ranges.

FIG. 13 is an explanatory view showing an example of the display imagethat displays the residual color difference information on the basis ofthe pickup image of the target camera that uses the correction LUT.

FIG. 14 is a flowchart showing a process for generating residual colordifference information by a display control apparatus according to asecond embodiment of the present invention.

FIG. 15 is a view showing an example of a combination of a pickup imageof the target camera that uses the correction LUT and a colordistribution image that is generated independently therefrom to showdistribution of residual color difference values.

FIG. 16 is a view showing an example of the color distribution imagethat shows the distribution of the residual color difference values of acase of applying this embodiment.

FIG. 17 is a view showing an example of a vector scope image that showsthe residual color difference information.

FIG. 18 is a flowchart showing a process for outputting a message when avalue of the residual color difference information is not less than athreshold.

DESCRIPTION OF THE EMBODIMENTS

Hereafter, embodiments according to the present invention will bedescribed in detail by referring to the drawings. However,configurations described in the following embodiments are just examples,and the scope of the present invention is not limited to theconfigurations described in the embodiments.

FIG. 1 is a configuration diagram showing a color difference correctionsystem that corrects color difference between a plurality of imagepickup apparatuses. The color difference correction system 1 in FIG. 1has a display control apparatus 200 according to a first embodiment ofthe present invention. A reference camera 100 that is an example of areference image pickup apparatus and a target camera 101 that is anexample of an adjustment image pickup apparatus are connected to thedisplay control apparatus 200 via image lines. The reference camera 100and target camera 101 pick up a same type object like a color chart.

The reference camera 100 outputs a pickup image to the display controlapparatus 200 through the image line. The target camera 101 outputs apickup image to the display control apparatus 200 through the imageline. The reference camera 100 and target camera 101 may pick up staticimages or may pick up video images.

The display control apparatus 200 compares input pickup images andgenerates a correction lookup table (LUT) for color matching that can beused by the target camera 101. When using the correction LUT generatedin this way, the target camera 101 can pick up an image of which colordifference from an image of the reference camera 100 is reduced. Theprocess that reduces the color difference between the images of theapparatuses using the correction LUT etc. is called color matching. Whenthe target camera 101 that is color-matched with the reference camera100 is used in the same image pickup environment with the referencecamera 100, a pickup image (an adjustment image) of which colors areclose to that of a pickup image (a reference image) of the referencecamera 100 can be obtained.

FIG. 2 is a block diagram showing a main configuration of the displaycontrol apparatus 200 in FIG. 1 . The reference camera 100 isconnectable with a first input terminal 221 through the image line. Thereference camera 101 is connectable with a second input terminal 222through the image line. A memory 223 stores programs that are executedby a controller 203 and various kinds of data. The memory 223 isconstituted by a nonvolatile semiconductor memory, an SSD, an HDD, aRAM, or the like. A work area that is used when running a program isallocated to the RAM. The nonvolatile semiconductor memory, SSD, HDD,etc. can record a program and data in a nonvolatile manner.

The controller 203 controls the entire display control apparatus 200,reads a program from the memory 223, and controls respective sections ofthe apparatus. The controller 203 is a CPU, for example.

The image reception unit 201 b receives an image from the target camera101 connected to the second input terminal 222 through the image lineand outputs it to an image capture unit 202 b. The image capture unit202 b captures the image received from the target camera 101. Then, theimage capture unit 202 b outputs the image captured to the controller203. The image capture unit 202 b can obtain an image before performingthe color matching and the image after performing the color matchingfrom the target camera 101 as an obtaining unit. The image capture unit202 b captures an image of one frame of a video image by recording it toa frame memory. Although an image of one frame may be an interlaceimage, a progressive image is preferable.

The image reception unit 201 a receives an image from the referencecamera 100 connected to the first input terminal 221 through the imageline and outputs it to an image capture unit 202 a. The image captureunit 202 a captures the image received from the reference camera 100.Then, the image capture unit 202 a outputs the image captured to thecontroller 203.

A UI operation unit 204 receives an operation from a user and outputs acorresponding instruction to the controller 203. For example, a pointingdevice, a pen tablet, etc. that are operated by a user are connected tothe UI operation unit 204. The UI operation unit 204 receives operationsto instruct the color matching, switching of a display content, etc.Moreover, the UI operation unit 204 receives an operation to select eachof rectangle color patches in an image. In this case, the UI operationunit 204 outputs a rectangle area from a start point to an end point ofa color patch selected by the user to the controller 203 as areainformation about the color patch.

The controller 203 achieves various control processes, such as a recordcontrol process, a display control process, and an image process, bycontrolling the respective sections of the display control apparatus200. For example, the controller 203 displays the image from thereference camera 100 and the image from the target camera 101 on thedisplay unit 211 side by side, as shown in FIG. 1 . The user can comparethe image from the reference camera 100 and the image from the targetcamera 101 by viewing the display unit 211.

When the area information about the color patch is input through the UIoperation unit 204, the controller 203 superimposes a rectangle frame onthe image currently displayed on the display unit 211. The controller203 may generate a warning screen and a message screen and may displaythem on the display unit 211. When generating the correction LUT, thecontroller 203 outputs the image from the reference camera 100, theimage from the target camera 101, and the area information about thecolor patches in the images to a correction LUT generation unit 205.

Moreover, when generating residual color difference information, thecontroller 203 outputs the image from the target camera 101 to a colorcoincidence determination unit 209. Moreover, the controller 203 maygenerate a display image for showing the residual color differenceinformation and may display it on the display unit 211. This displayimage corresponds to display information generated on the basis of theresidual color difference information. Moreover, the controller 203switches a display content on the display unit 211 in accordance with auser operation through the UI operation unit 204. Thereby, thecontroller 203 can switch generation of the correction LUT and displayof the residual color difference information on the basis of the useroperation.

The correction LUT generation unit 205 obtains the information forgenerating the correction LUT from the controller 203 and generates thecorrection LUT for matching the colors of the image picked up by thetarget camera 101 with the colors of the image picked up by thereference camera 100. The information obtained from the controller 203includes the image from the reference camera 100, the image from thetarget camera 101, and the area information about the color patchescorresponding to these images. Then, the correction LUT generation unit205 outputs the correction LUT generated to a correction LUT output unit206. Moreover, the correction LUT generation unit 205 outputs the RGBvalues of the color patches in the images from the cameras and the imagefrom the target camera 101, which are used to generate the correctionLUT, to a camera-characteristic-information storage unit 207.

The correction LUT output unit 206 converts the correction LUT inputfrom the correction LUT generation unit 205 into a file of a format thatthe target camera 101 can import. For example, the file of thecorrection LUT generated by the correction LUT output unit 206 may berecorded in a portable medium (not shown) and may be imported to thetarget camera 101 by copying. Thereby, the target camera 101 can pick upa color-matched image to which the color matching is applied using thecorrection LUT. It should be noted that the correction LUT output unit206 may transmit the file of the correction LUT to the target camera 101by wireless communication etc. Moreover, when the target camera 101 andthe display control apparatus 200 are connected via a LAN cable, thecorrection LUT output unit 206 may transmit the file of the correctionLUT to the target camera 101 via the LAN cable.

The camera-characteristic-information storage unit 207 records and holdscamera characteristic information. The unit 207 may be constituted by astorage medium like an independent RAM or may function by using a partof the memory 223. The camera characteristic information includesvarious kinds of information about the color matching of the targetcamera 101. The camera characteristic information may include theinformation about the reference camera 100 and the information about thetarget camera 101 that are related to the color matching, for example.Moreover, the camera characteristic information may include the RGBvalues of the color patches obtained in performing the color matching ofthe reference camera 100 and the target camera 101, for example.Moreover, the camera characteristic information may include the imagefrom the reference camera 100 used for the color matching with thetarget camera 101.

A residual-color-difference-information generation unit 208 generatesresidual color difference information on the basis of the cameracharacteristic information held by the camera-characteristic-informationstorage unit 207 by calculating color difference between the image fromthe target camera 101 and the image from the reference camera 100 on apixel basis. Then, the residual-color-difference-information generationunit 208 may generate the residual color difference information aboutthe color difference that remains in the image from the target camera101 after the color matching using the camera characteristic informationheld by the camera-characteristic-information storage unit 207. Theresidual-color-difference-information generation unit 208 may calculatethe color difference between each pixel of the image from the targetcamera 101 and each pixel of the held image from the reference camera100. Thereby, the residual-color-difference-information generation unit208, as a residual color difference generation means, generates theresidual color difference information showing the residual colordifference that remains in the image from the target camera 101 thatperforms the color matching as the difference from the image from thereference camera 100. The residual color difference information showsthe residual color difference that remains between each pixel value ofthe image from the target camera 101 after performing the color matchingand each pixel value of the image from the reference camera 100.

A color coincidence determination unit 209 determines a colorcoincidence degree between each pixel value of the image from the targetcamera 101 and each pixel value of the image from the reference camera100. The color coincidence determination unit 209 outputs each pixelvalue of the image from the target camera 101 to theresidual-color-difference-information generation unit 208 and determinesthe color coincidence degree on the basis of the residual colordifference information generated by theresidual-color-difference-information generation unit 208. Acolor-coincidence-information generation unit 210 generates a displayimage for showing the residual color difference information about theimage from the target camera 101 that performs the color matching.

For example, the color-coincidence-information generation unit 210 maygenerate the display image for showing the residual color differenceinformation by converting each pixel value of the image from thecorresponding target camera 101 in accordance with the color coincidencedegree determined by the color coincidence determination unit 209. Inthis case, when the color coincidence degree of the pixel is lower thana threshold, the color-coincidence-information generation unit 210 mayconvert the pixel value of the pixel into a pixel value that shows theresidual color difference. Thereby, the color-coincidence-informationgeneration unit 210, as a display information generation means,generates display information based on the residual color differenceinformation. The display unit 211 has a monitor, for example, anddisplays an image on the monitor. For example, the display unit 211 maydisplay the warning screen received from the controller 203, aresidual-color-difference value Display image received from thecolor-coincidence-information generation unit 210, etc.

It should be noted that the configuration of the image processingapparatus is not limited to the configuration shown in FIG. 2 . Forexample, each control process can be executed by a single hardware unitor a plurality of hardware units may function as a single means as awhole by sharing a process. Moreover, a single hardware unit mayfunction as a plurality of means depending on programs to run. This isthe same about a storage process. Various kinds of data may be stored toa single hardware unit like the memory 223. Or a plurality of recordingmedia may be prepared depending on various kinds of storage processes.Moreover, the display unit 211 is not necessarily mounted in the displaycontrol apparatus 200. The display control apparatus 200 should have atleast an interface with the display unit 211.

Hereinafter, a process that generates the correction LUT used by thetarget camera 101 for the color matching is described first. FIG. 3 is aflowchart showing the process that the display control apparatus 200generates the correction LUT for matching a color characteristic of thetarget camera 101 to a color characteristic of the reference camera 100by comparing the image from the reference camera 100 and the image fromthe target camera 101. A user operates the UI operation unit 204 togenerate the correction LUT. For example, the user selects an item of“Generate color matching LUT” in a menu screen. The controller 203starts the process to generate the correction LUT by the display controlapparatus 200 in response to the input operation through the UIoperation unit 204.

FIG. 4 is a view showing an example of a combination of a pickup image400 a of the reference camera 100 and a pickup image 400 b of the targetcamera 101 that are currently displayed on the display unit 211. Each ofthe images 400 a and 400 b in FIG. 4 has predetermined color patches401, 402, and 403. The color patch 401 is red. The color patch 402 isgreen. The color patch 403 is blue. The user operates the UI operationunit 204 to generate the correction LUT.

The controller 203 selects areas of the color patches 401, 402, and 403in the images 400 a and 400 b on the basis of the user operations inputthrough the UI operation unit 204. After that, the controller 203controls the respective sections of the display control apparatus 200 toexecute the process in FIG. 3 . The controller 203 outputs the areainformation about the selected color patches and the images 400 a and400 b to the correction LUT generation unit 205. Thereby, this controlis started. Although it is preferable to include the predetermined colorpatches 401, 402, and 403 in the images 400 a and 400 b that arecompared to generate the correction LUT, images that do not include suchcolor patches can be also used to generate the correction LUT.

In a step S301 in FIG. 3 , the correction LUT generation unit 205extracts the RGB values showing colors of the color patches in theimages 400 a and 400 b. The correction LUT generation unit 205 mayextract the RGB values using the image 400 a from the reference camera100, the image 400 b form the target camera 101, and the areainformation about the color patches 401, 402, and 403 that are receivedfrom the controller 203. Then, the correction LUT generation unit 205stores the extracted RGB values of the color patches of the images 400 aand 400 b to the camera-characteristic-information storage unit 207 ascamera characteristic information. The correction LUT generation unit205 may extract averages of pixel values in the areas of the designatedcolor patches 401, 402, and 403 as the RGB values or may extract thepixel values of the centers of the areas as the RGB values.

In a step S302, the correction LUT generation unit 205 converts the RGBvalues of the color patches 401, 402, and 403 into XYZ values. Thecorrection LUT generation unit 205 may convert the RGB values into theXYZ values using the following formula 1, for example. The followingformula 1 is a determinant that converts the RGB values into the XYZvalues using a conversion matrix (an RGB-to-XYZ conversion matrix). Forexample, the RGB-to-XYZ conversion matrix can be generated bycalculation using an xy coordinate of a display color gamut of thedisplay control apparatus 200 and an xy coordinate of a white point.Moreover, it is preferable to substitute values that are obtained bynormalizing the RGB values of the color patches 401, 402, and 403 intovalues r, g, and b of the following formula 1. Thereby, the RGB valuesof the color patches 401, 402, and 403 of the images in FIG. 5 areconverted into the XYZ values of the color patches 401, 402, and 403shown in FIG. 6 , for example.

$\begin{matrix}{\begin{bmatrix}X \\Y \\Z\end{bmatrix} = {\begin{bmatrix}{{RGB} - {to} - {XYZ}} \\{{Conversion}{Matri}x}\end{bmatrix}\begin{bmatrix}r \\g \\b\end{bmatrix}}} & {{Formula}1}\end{matrix}$

FIG. 5 is a view showing an example of a combination of the RGB valuesof the color patches 401 in the pickup images 400 a and 400 b in FIG. 4. FIG. 6 is a view showing an example of a combination of the XYZ valuesof the color patches obtained on the basis of the RGB values of thecolor patches 401, 402, and 403 in FIG. 4 . The XYZ values convertedfrom the RGB values of the color patches 401, 402, and 403 in the imagefrom the reference camera 100 shall be an arithmetic matrix R. The XYZvalues converted from the RGB values of the color patches 401, 402, and403 in the image from the target camera 101 shall be an arithmeticmatrix T.

In a step S303 in FIG. 3 , the correction LUT generation unit 205calculates a correction matrix M for matching the color characteristicof the target camera 101 with the color characteristic of the referencecamera 100. The correction matrix M is a matrix for correcting the XYZvalues of the color patches in the image from the target camera 101 tothe XYZ values of the color patches in the image from the referencecamera 100. The correction matrix M can be calculated by the followingformula 2, for example.

[Correction Matrix M]=[Arithmetic Matrix R][Arithmetic Matrix T]⁻¹  Formula 2

In a step S304, the correction LUT generation unit 205 generates thecorrection LUT using the correction matrix M calculated in the stepS303. The correction LUT generation unit 205 outputs the correction LUTgenerated to the correction LUT output unit 206. Thereby finishes theprocess of FIG. 3 .

FIG. 7 is an explanatory view of an example of the correction LUTgenerated by the display control apparatus 200 in FIG. 1 . Thecorrection LUT is used to convert the RGB values (In) at the left sidein FIG. 7 into the XYZ values (Out) at the right side in FIG. 7 . Thecorrection LUT may consist of lattice points of 17*17*17. The RGB values(In) of each lattice point of the correction LUT can be converted intothe XYZ values using the RGB-to-XYZ conversion matrix mentioned above.Then, corrected XYZ values X_(C), Y_(C), and Z_(C) of such a latticepoint are calculable by the following formula 3 using the XYZ values X,Y, Z of the lattice point and the correction matrix M mentioned above.Moreover, the corrected RGB values (Out) corresponding to the RGB values(In) of each lattice point of the correction LUT are calculated usingthe corrected XYZ values X_(C), Y_(C), and Z_(C) of the lattice pointand an inverse matrix of the RGB-to-XYZ conversion matrix. In thecorrection LUT in FIG. 7 , the RGB values (In) and RGB values (Out) areassociated by such a process.

$\begin{matrix}{\begin{bmatrix}X_{C} \\Y_{C} \\Z_{C}\end{bmatrix} = {\left\lbrack {{Correction}{Matrix}M} \right\rbrack\begin{bmatrix}X \\Y \\Z\end{bmatrix}}} & {{Formula}3}\end{matrix}$

Moreover, the correction LUT generation unit 205 calculates anarithmetic matrix S used in a flow of a residual color differencecalculation process mentioned later by the following formula 4 using theabove-mentioned arithmetic matrix T and the correction matrix M. Thecorrection LUT generation unit 205 stores the calculated arithmeticmatrix S in the camera-characteristic-information storage unit 207.

[Arithmetic Matrix S]=[Correction Matrix M][Arithmetic Matix T]  Formula4

The above process enables the display control apparatus 200 to generatethe correction LUT that reduces the color difference of the targetcamera 101 and improves the coincidence degree with the colorcharacteristic of the reference camera 100. The target camera 101 towhich such color matching is applied and the reference camera 100 can beused to pick up the same object as shown in FIG. 1 by reducing the colordifference therebetween. Each of the target camera 101 and referencecamera 100 picks up a static image or a video image by receiving lightentering through an optical system using an image sensor like a CCDsensor or a CMOS sensor, for example. There is a difference of a lightreceiving characteristic etc. in image sensors. In such a case, it isexpectable that the colors of the pickup image of the target camera 101and the colors of the pickup image of the reference camera 100 coincidesatisfactorily by using the above-mentioned correction LUT to the imagegeneration by the target camera 101.

However, even if the target camera 101 uses such a correction LUT, notall the colors of the pickup image of the target camera 101 match thecolors of the pickup image of the reference camera 100. On a site wherea plurality of image pickup apparatuses are used actually, colordifference may remain in some objects even if the above-mentionedcorrection LUT is used. Generally, although large color difference valueDoes not remain in the entire color space, color difference that isrelatively easy to confirm visually may remain in some colors.

In this way, the color difference that remains also after thepredetermined color matching, such as an application of the correctionLUT, is called residual color difference. When there is such residualcolor difference, it is difficult for a user to find the residual colordifference by comparing the pickup image of the reference camera 100with the pickup image of the target camera 101 to which the colormatching has been applied by visual observation.

On a site where a plurality of image pickup apparatuses are used, it isrequired to easily discriminate the residual color difference that mayremain between the plurality of image pickup apparatuses. Accordingly,the display control apparatus 200 of this embodiment generates theabove-mentioned correction LUT and further generates residual colordifference information corresponding to the coincidence degree of thecolor characteristic of the target camera 101 after the color matchingusing the correction LUT. Then, the display control apparatus 200supplies the residual color difference information to a user bydisplaying it so as to be easily discriminated.

FIG. 8 is a flowchart showing a process for generating the residualcolor difference information about the target camera 101 that reads thecorrection LUT generated by the process of FIG. 3 . The target camera101 outputs the image to which the color matching is applied by usingthe read correction LUT to the display control apparatus 200. The useroperates the UI operation unit 204 after generating the correction LUT.For example, the user selects an item of “Show color difference” fromthe menu screen. The controller 203 starts the residual color differenceinformation generation process in FIG. 8 on the basis of an inputoperation through the UI operation unit 204. The controller 203 outputsthe color-matched image that is picked up by the target camera 101 usingthe correction LUT to the color coincidence determination unit 209.

In a step S801, the color coincidence determination unit 209 extractsthe RGB values of the color patches from the image on the basis of acolor-matched image of the target camera 101 received from thecontroller 203 and the area information about the color patches. Itshould be noted that examples of the RGB values of the color patchesobtained here are shown in FIG. 9 FIG. 9 is a view showing an example ofa combination of RGB values of the color patches in the image from thetarget camera 101 after the color matching. Since the color matching isperformed, the RGB values of the color patches in FIG. 9 are differentfrom the RGB values of the color patches from the target camera 101 inFIG. 5 .

In a step S802, the color coincidence determination unit 209 convertsthe RGB values of the color patches into XYZ values. The colorcoincidence determination unit 209 outputs the generated XYZ values ofthe color patches to the residual-color-difference-informationgeneration unit 208. The conversion process by the color coincidencedetermination unit 209 may be the same as the conversion process by thecorrection LUT generation unit 205 in the step S302 mentioned above.FIG. 10 is a view showing an example of a combination of XYZ valuesafter the color matching that are obtained on the basis of the RGBvalues of the color patches in FIG. 9 . The XYZ values of the colorpatches obtained here are different from the XYZ values from the targetcamera 101 before the color matching shown in FIG. 6 . Then, the XYZvalues of the color patches obtained here are used as a 3-row and3-column arithmetic matrix H.

In a step S803, the residual-color-difference-information generationunit 208 calculates an error correction matrix GM and stores it to thecamera-characteristic-information storage unit 207. Theresidual-color-difference-information generation unit 208 may calculatethe error correction matrix GM on the basis of the XYZ values of thecolor patches received from the color coincidence determination unit 209and the arithmetic matrix S held in thecamera-characteristic-information storage unit 207. It should be notedthat the error correction matrix GM shows the residual color differencethat remains after the color matching. Thereby finishes the process ofFIG. 8 .

The error correction matrix GM is a correction matrix for correcting theresidual color difference. The error correction matrix GM can becalculated by the following formula 5 from the arithmetic matrix H,which shows the XYZ values of the color patches actually picked up bythe target camera 101 after the color matching, and the arithmeticmatrix S that is found by the above-mentioned formula 4.

[Error Correction Matrix GM]=[Arithmetic Matrix S][Arithmetic Matrix H]⁻¹  Formula 5

The display control apparatus 200 can generate the residual colordifference information showing the color difference that remains in theimage from the target camera 101 after the color matching by the aboveprocess. The residual color difference information corresponds to theerror correction matrix GM. The residual color difference information isinformation about the value corresponding to the color coincidencedegree in the image. The residual color difference information shows thecolor difference that remains in the adjustment image from the targetcamera 101 that performs the color matching as the difference from thereference image from the reference camera 100. Then, the residual colordifference information may be recorded in the memory 223 that functionsas the camera-characteristic-information storage unit 207, for example.

Next, the color-coincidence-information generation unit 210 generatesthe display image for displaying the residual color differenceinformation about the image from the target camera 101 that performs thecolor matching on the display unit 211 on the basis of the residualcolor difference information generated. A part or the whole of theprocess by the color-coincidence-information generation unit 210 forgenerating the display image may be executed by the color coincidencedetermination unit 209. For example, the color coincidence determinationunit 209 may determine the color coincidence degree between the pixelvalue of the image from the reference camera 100 and the pixel value ofthe image from the target camera 101.

FIG. 11 is a flowchart showing a process for generating the displayimage for displaying the residual color difference information. Thecamera-characteristic-information storage unit 207 holds the residualcolor difference information that shows the residual color differencethat remains in the adjustment image from the target camera 101 thatperforms the color matching as the difference from the reference imagefrom the reference camera 100. When the UI operation unit 204 receivesan instruction based on a predetermined user operation, the controller203 instructs generation of the display image to thecolor-coincidence-information generation unit 210 through the colorcoincidence determination unit 209 in order to display the residualcolor difference information on the display unit 211. Thereby, thecolor-coincidence-information generation unit 210 starts the process ofFIG. 11 .

In a step S1101, the color-coincidence-information generation unit 210obtains a vertical pixel count (the number of pixels in a verticaldirection) of the image that is picked up by the target camera 101 andis processed by the color coincidence determination unit 209, and startsa first loop process. In the first loop process, a loop variable “i” isincremented by one for every loop and the loop process is finished whenthe loop variable “i” reaches the vertical pixel count. In a step S1102,the color-coincidence-information generation unit 210 obtains ahorizontal pixel count (the number of pixels in a horizontal direction)of the image that is picked up by the target camera 101 and is processedby the color coincidence determination unit 209, and starts a secondloop process. In the second loop process, a loop variable “j” isincremented for every loop by one and the loop process is finished whenthe loop variable “j” reaches the horizontal pixel count.

In a step S1103, the color-coincidence-information generation unit 210obtains the RGB values of a pixel at a position (i, j) in the image fromthe target camera 101 that performs the color matching. In a step S1104,the color-coincidence-information generation unit 210 outputs theobtained RGB values of the pixel to theresidual-color-difference-information generation unit 208 through thecolor coincidence determination unit 209. Theresidual-color-difference-information generation unit 208 compares thecolor of the obtained RGB values of the pixel concerned with the colorof the pixel at the corresponding position in the image from thereference camera 100, and calculates the residual color difference valueof the pixel concerned in the image from the target camera 101 thatperforms the color matching.

The color-coincidence-information generation unit 210 obtains theresidual color difference information from theresidual-color-difference-information generation unit 208 through thecolor coincidence determination unit 209. Theresidual-color-difference-information generation unit 208 converts theRGB values obtained through the color coincidence determination unit 209into the XYZ values using an RGB-to-XYZ conversion matrix similar tothat used in the step S302. After that, theresidual-color-difference-information generation unit 208 calculatesinherent corrected XYZ values X_(TC), Y_(TC), and Z_(TC), which areobtained when the correction LUT is correctly applied, by using theconverted XYZ values and the error correction matrix GM that iscalculated in the step S803 by the following formula 6. Then, theresidual-color-difference-information generation unit 208 calculates theresidual color difference value D by the following formula 7 by usingthe inherent corrected XYZ values X_(TC), Y_(TC), and Z_(TC), and thevalues X, Y, and Z that are obtained by XYZ-converting the RGB valuesobtained from the target camera 101. It should be noted that thearithmetic method of the residual color difference value D shown here isan example. The residual-color-difference-information generation unit208 may calculate the residual color difference value D by using the RGBvalues obtained, for example.

$\begin{matrix}{\begin{bmatrix}X_{TC} \\Y_{TC} \\Z_{TC}\end{bmatrix} = {\begin{bmatrix}{{Error}{Corre}ction} \\{{Matrix}{GM}}\end{bmatrix}\begin{bmatrix}X \\Y \\Z\end{bmatrix}}} & {{Formula}6}\end{matrix}$ $\begin{matrix}{D = \sqrt{\left( {X_{TC} - X} \right)^{2} + \left( {Y_{TC} - Y} \right)^{2} + \left( {Z_{TC} - Z} \right)^{2}}} & {{Formula}7}\end{matrix}$

In a step S1105, the color-coincidence-information generation unit 210determines whether the residual color difference value D received fromthe residual-color-difference-information generation unit 208 is lessthan a threshold. The threshold of the residual color difference valueis determined on the basis of the range of value that is allowable asthe residual color difference. At this time point, thecolor-coincidence-information generation unit 210 grasps the positionand the residual color difference value D of the pixel that is a targetof the determination process. When the residual color difference value Dis less than the threshold, the color-coincidence-information generationunit 210 proceeds with the process to a step S1106. When the residualcolor difference value D is not less than the threshold, thecolor-coincidence-information generation unit 210 proceeds with theprocess to a step S1107.

In the step S1106, the color-coincidence-information generation unit 210executes the process that maintains the pixel value at the position ofthe pixel that is a target of the determination process in the imagefrom the target camera 101 after the color matching. That is, thecolor-coincidence-information generation unit 210 does not convert thepixel value at the position of the pixel that is a target of thedetermination process. After that, the color-coincidence-informationgeneration unit 210 proceeds with the process to a step S1108.

In the step S1107, the color-coincidence-information generation unit 210converts the pixel value at the position of the pixel that is a targetof the determination process in the image from the target camera 101after the color matching into a pixel value for displaying the residualcolor difference information. The pixel value for displaying theresidual color difference information represents a predetermined colorthat is easily distinguished from other pixels in the image from thetarget camera 101 after the color matching. After that, thecolor-coincidence-information generation unit 210 proceeds with theprocess to a step S1108.

In the step S1108, the color-coincidence-information generation unit 210determines finishing about the second loop process started in the stepS1102. When the loop variable “j” does not reach the horizontal pixelcount, the color-coincidence-information generation unit 210 returns theprocess to the step S1102 and increments the variable “j” by one. Thecolor-coincidence-information generation unit 210 repeats the processfrom the step S1102 to the step S1108 until the loop variable “j”reaches the horizontal pixel count of the image. Thecolor-coincidence-information generation unit 210 repeats the secondloop process from the step S1102 to the step S1108 by the horizontalpixel count of the image from the target camera 101 after the colormatching. Thereby, the color-coincidence-information generation unit 210executes the conversion process based on the residual color differenceinformation about the pixels on one line aligned in the horizontaldirection in the image from the target camera 101 after the colormatching. The color-coincidence-information generation unit 210 proceedswith the process to a step S1109, when the loop variable “j” reaches thehorizontal pixel count.

In the step S1109, the color-coincidence-information generation unit 210determines finishing about the first loop process started in the stepS1101. When the loop variable “i” does not reach the vertical pixelcount, the color-coincidence-information generation unit 210 returns theprocess to the step S1101 and increments the variable “i” by one. Thecolor-coincidence-information generation unit 210 repeats the processfrom the step S1101 to the step S1109 until the loop variable “i”reaches the vertical pixel count of the image. Thecolor-coincidence-information generation unit 210 repeats the first loopprocess from the step S1101 to the step S1109 by the vertical pixelcount of the image from the target camera 101 after the color matching.Thereby, the color-coincidence-information generation unit 210 executesthe conversion process based on the residual color differenceinformation about the pixels on lines aligned in the vertical directionin the image from the target camera 101 after the color matching. Whenthe loop variable “i” reaches the vertical pixel count, thecolor-coincidence-information generation unit 210 finishes this process.

Thereby, the color-coincidence-information generation unit 210 generatesthe image in which pixel values of a part of pixels of the image fromthe target camera 101 after the color matching are converted into thepixel value that displays the residual color difference information asthe display image that displays the residual color differenceinformation. In this display image, a part where the residual colordifference more than the threshold occurs in the image from the targetcamera 101 after the color matching is displayed by the pixel value thatdisplays the residual color difference information. Thecolor-coincidence-information generation unit 210 outputs the generateddisplay image to the display unit 211. The display unit 211 displays thedisplay image generated by the color-coincidence-information generationunit 210. The user can easily visually confirm the part where theresidual color difference occurs in the image that is picked up by thetarget camera 101 after the color matching and is displayed on thedisplay unit 211 because the part is displayed by the pixel value thatdisplays the residual color difference information.

FIG. 12 is a table showing correspondence relations between ranges ofthe residual color difference value defined by the residual colordifference information and conversion colors used as colors of pixelsincluded in the respective ranges. In FIG. 12 , the residual colordifference value D is classified to three steps. Then, when the residualcolor difference value D is more than 0 and less than 1, thecolor-coincidence-information generation unit 210 determines that thedifference value D is less than the threshold and does not convert thepixel value of the target position. When the residual color differencevalue D is more than 1 and less than 2, thecolor-coincidence-information generation unit 210 determines that thedifference value D is not less than the threshold and converts the pixelvalue of the target position into the pixel value (R, G, B=128, 0, 0)that displays the residual color difference information. Moreover, whenthe residual color difference value D is two or more, thecolor-coincidence-information generation unit 210 determines that thedifference value D is not less than the threshold and converts the pixelvalue of the target position into the pixel value (R, G, B=255, 0, 0)that displays the residual color difference information. A red tone ofthe pixel value (R, G, B=255, 0, 0) is stronger than the pixel value (R,G, B=128, 0, 0). In the display image, the color of the part where theresidual color difference information showing that the residual colordifference value is more than the threshold in the image from the targetcamera 101 that performs the color matching is converted into thedifferent color depending on the value of the residual color differenceinformation. The table of the correspondence relations in FIG. 12 isrecorded in the memory 223. In this case, thecolor-coincidence-information generation unit 210 obtains the residualcolor difference and the threshold compared from the memory 223 andexecutes the determination in the step S1105 in accordance with thetable of the correspondence relations in FIG. 12 .

FIG. 13 is an explanatory view showing an example of the display imagethat displays the residual color difference information on the basis ofthe pickup image of the target camera 101 that uses the correction LUT.The display image in FIG. 13 is displayed on the display unit 211. Inthe display image in FIG. 13 , its partial areas are displayed by thepixel value that displays the residual color difference information.When such a display image is displayed on the display unit 211, the usercan determine the presence and degree of occurrence of the residualcolor difference intuitively only by glancing at the display unit 211.The user can immediately execute a necessary process that regenerates oradjusts the correction LUT, for example, on the basis of thedetermination. The user is not required to compare the pickup image fromthe target camera 101 that uses the correction LUT with the pickup imagefrom the reference camera 100 that are displayed on the display unit 211so as to discriminate the minute residual color difference that remainsbetween them by visual observation.

As mentioned above, in this embodiment, the color coincidence degreebetween the pickup image of the reference camera 100 and the pickupimage of the target camera 101 can be determined based on theinformation about the residual color difference between the cameras, andthe residual color difference information that is the determinationresult can be explicitly displayed in the image from the target camera101. The color difference correction system 1 of this embodiment can beused in order to discriminate easily the residual color differencebetween the image pickup apparatuses at the site where the referencecamera 100 and the target camera 101 are used.

It should be noted that the threshold of the residual color differencevalue and the converted pixel value may be designated by the userthrough the UI operation unit 204. The user can designate so that apixel of which the residual color difference value is less than thethreshold will be displayed in monochrome. In this case, the displayimage of which a part where the residual color difference value is morethan the threshold is colored will be displayed, which enables the userto intuitively discriminate the color coincidence degree.

Moreover, in the above-mentioned embodiment, thecolor-coincidence-information generation unit 210 generates the displayimage by converting the pixel value of the color-matched image from thetarget camera 101 into the pixel value that displays the residual colordifference. In addition, for example, the color-coincidence-informationgeneration unit 210 may generate the image for displaying the residualcolor difference as the display image. The color-coincidence-informationgeneration unit 210 may display the display image for displaying theresidual color difference on the display unit 211 by superimposing onthe color-matched image from the target camera 101.

Moreover, the above-mentioned embodiment describes the method forcalculating the residual color difference by calculating the errorcorrection matrix using the red, green, and blue color patches 401, 402,and 403. In addition, for example, the color-coincidence-informationgeneration unit 210 may calculate the residual color difference on thebasis of the colors at the vertex of the lattice points of thecorrection LUT measured by the reference camera 100 and the targetcamera 101. Furthermore, the color-coincidence-information generationunit 210 may calculate the residual color difference using a table thatstores the residual color difference values of all the colors. The tableis generated by picking up all the colors by the reference camera 100and the target camera 101 beforehand and is held in thecamera-characteristic-information storage unit 207.

Next, the color difference correction system 1 including the displaycontrol apparatus 200 according to a second embodiment of the presentinvention will be described. Hereinafter, differences from the firstembodiment are mainly described. The display control apparatus 200 ofthis embodiment differs from the first embodiment in the process of thecolor-coincidence-information generation unit 210. Moreover, it isdifferent from the first embodiment in that a display image that isgenerated by the color-coincidence-information generation unit 210 onthe basis of the color-matched image from the target camera 101 is acolor distribution image that shows distribution of the residual colordifference values.

FIG. 14 is a flowchart showing a process for generating residual colordifference information by the display control apparatus 200 according tothe second embodiment of the present invention. In the process in FIG.14 , the color-coincidence-information generation unit 210 generatesdistribution information about the residual color difference values bycalculating a color coincidence degree (a residual color differencevalue) of each pixel of a color-matched image (an image to which acorrection LUT is applied) from the target camera 101 with respect to acorresponding pixel of an image from the reference camera 100. When theUI operation unit 204 receives an instruction based on a predetermineduser operation, the controller 203 instructs generation of the displayimage to the color-coincidence-information generation unit 210 throughthe color coincidence determination unit 209 in order to display theresidual color difference information on the display unit 211. Thereby,the color-coincidence-information generation unit 210 executes theprocess of FIG. 14 .

In a step S1501, the color-coincidence-information generation unit 210obtains the vertical pixel count of the image that is picked up by thetarget camera 101 and is processed by the color coincidencedetermination unit 209, and starts a first loop process. In the firstloop process, a loop variable “i” is incremented by one for every loopand the loop process is finished when the loop variable “i” reaches thevertical pixel count. In a step S1502, the color-coincidence-informationgeneration unit 210 obtains a horizontal pixel count of the image thatis picked up by the target camera 101 and is processed by the colorcoincidence determination unit 209, and starts a second loop process. Inthe second loop process, a loop variable “j” is incremented for everyloop by one and the loop process is finished when the loop variable “j”reaches the horizontal pixel count.

In a step S1503, the color-coincidence-information generation unit 210obtains the RGB values of a pixel at a position (i, j) in the image fromthe target camera 101 that performs the color matching. In a step S1504,the color-coincidence-information generation unit 210 outputs theobtained RGB values of the pixel to theresidual-color-difference-information generation unit 208 through thecolor coincidence determination unit 209. Theresidual-color-difference-information generation unit 208 compares thecolor of the obtained RGB values of the pixel concerned with the colorof the pixel at the corresponding position in the image from thereference camera 100, and calculates the residual color difference valueof the pixel concerned in the image from the target camera 101 thatperforms the color matching. The color-coincidence-informationgeneration unit 210 obtains the residual color difference informationfrom the residual-color-difference-information generation unit 208through the color coincidence determination unit 209.

In a step S1505, the color-coincidence-information generation unit 210receives the residual color difference and the pixel position in theimage at which the residual color difference is calculated from thecolor coincidence determination unit 209, and generates the displayimage displaying the residual color difference. In a step S1506, thecolor-coincidence-information generation unit 210 determines finishingabout the second loop process started in the step S1502. When the loopvariable “j” does not reach the horizontal pixel count, thecolor-coincidence-information generation unit 210 returns the process tothe step S1502 and increments the variable “j” by one. Thecolor-coincidence-information generation unit 210 repeats the processfrom the step S1502 to the step S1506 until the loop variable “j”reaches the horizontal pixel count of the image. Thecolor-coincidence-information generation unit 210 repeats the secondloop process from the step S1502 to the step S1506 by the horizontalpixel count of the image from the target camera 101 after the colormatching. Thereby, the color-coincidence-information generation unit 210plots the residual color difference values on the color distributionimage showing distribution of the residual color difference values aboutthe pixels on one line aligned in the horizontal direction in the imagefrom the target camera 101 after the color matching. Thecolor-coincidence-information generation unit 210 proceeds with theprocess to a step S1507, when the loop variable “j” reaches thehorizontal pixel count.

In the step S1507, the color-coincidence-information generation unit 210determines finishing about the first loop process started in the stepS1501. When the loop variable “i” does not reach the vertical pixelcount, the color-coincidence-information generation unit 210 returns theprocess to the step S1501 and increments the variable “i” by one. Thecolor-coincidence-information generation unit 210 repeats the processfrom the step S1501 to the step S1507 until the loop variable “i”reaches the vertical pixel count of the image. Thecolor-coincidence-information generation unit 210 repeats the first loopprocess from the step S1501 to the step S1507 by the vertical pixelcount of the image from the target camera 101 after the color matching.Thereby, the color-coincidence-information generation unit 210 executesthe conversion process based on the residual color differenceinformation about the pixels on lines aligned in the vertical directionin the image from the target camera 101 after the color matching. Whenthe loop variable “i” reaches the vertical pixel count, thecolor-coincidence-information generation unit 210 finishes this process.

Thereby, the color-coincidence-information generation unit 210 cangenerate the color distribution image showing distribution of theresidual color difference values as the display image that displays theresidual color difference information. The color-coincidence-informationgeneration unit 210 outputs the generated color distribution imageshowing the distribution of the residual color difference values to thedisplay unit 211. The display unit 211 displays the color distributionimage showing the distribution of the residual color difference values.

FIG. 15 is a view showing an example of a combination of a pickup imageof the target camera 101 that uses the correction LUT and a colordistribution image that is generated independently therefrom to show thedistribution of the residual color difference values. Thecolor-coincidence-information generation unit 210 sequentially obtainsthe residual color difference information about each pixel of the pickupimage, which is shown in an upper part in FIG. 15 , of the target camera101 that uses the correction LUT. Then, thecolor-coincidence-information generation unit 210 plots the residualcolor difference value of the pixel at the obtained position on thecolor distribution image showing the distribution of the residual colordifference values shown in a lower part in FIG. 15 . A background imageof the color distribution image showing the distribution of the residualcolor difference values may be stored in the memory 223 beforehand.Then, the horizontal axis of the color distribution image showing thedistribution of the residual color difference values shows a horizontalposition in the image. A vertical axis shows the residual colordifference value. In this case, the color-coincidence-informationgeneration unit 210 plots a point showing the residual color differencevalue at the position on the vertical axis corresponding to the residualcolor difference value of the pixel at the obtained position. Thecolor-coincidence-information generation unit 210 may repeat plotting ofpoints at positions corresponding to the residual color differencevalues about the pixels on one line in the horizontal direction in thepickup image of the target camera 101 that uses the correction LUT.

FIG. 16 is a view showing an example of the color distribution imageshowing the distribution of the residual color difference values of acase of applying this embodiment. In the color distribution imageshowing the distribution of the residual color difference values in FIG.16 , the large residual color difference occurs in the left part in theimage mainly. Moreover, the maximum residual color difference valuereaches 2.0. The user can intuitively grasp a position and a degree ofthe residual color difference in the pickup image of the target camera101 that uses the correction LUT by only visually confirming the colordistribution image in FIG. 16 showing the distribution of the residualcolor difference values. Moreover, the color distribution image showingthe distribution of the residual color difference values shown in FIG.16 displays a color phase designated by the user. In addition, forexample, the color distribution image showing the distribution of theresidual color difference values may be displayed by superimposing aplurality of color phases by using different colors.

As mentioned above, in this embodiment, the color coincidence degreebetween the image from the reference camera 100 and the image from thetarget camera 101 is determined, and the color distribution imageshowing the distribution of the residual color difference values betweenthese images is generated and displayed. The user can intuitivelydiscriminate presence of the residual color difference and its positionin the image by visually confirming the color distribution image showingthe distribution of the residual color difference values.

The color-coincidence-information generation unit 210 may generate adisplay image other than the color distribution image showing thedistribution of the residual color difference values mentioned above asa display image that displays the residual color difference. Forexample, the color-coincidence-information generation unit 210 maygenerate the display image that totals up a ratio of pixels of which theresidual color difference values are more than a certain value for eachline in the horizontal direction of the image as a display image fordisplaying residual color difference. Moreover, thecolor-coincidence-information generation unit 210 may display thedistribution information of the residual color difference values ofpositions of pixels for each line in the vertical direction rather thanin the horizontal direction. Moreover, the color-coincidence-informationgeneration unit 210 may not necessarily generate the color distributionimage showing the distribution of the residual color difference valuesabout all the pixels of the color-matched image of the target camera101. The color-coincidence-information generation unit 210 may generatethe color distribution image showing the distribution of the residualcolor difference values about the specific color that is designated bythe user, for example. In this case, the user can check the distributionof the residual color difference values for each color designated whileswitching the color to designate. Moreover, thecolor-coincidence-information generation unit 210 may display theresidual color difference values in a vector scope image as a displayimage that displays the residual color difference values.

FIG. 17 is a view showing an example of the vector scope image thatdisplays the residual color difference information about the image fromthe target camera 101 that performs the color matching. The vector scopeimage shows a color phase and saturation of each pixel in an imagebasically. The color-coincidence-information generation unit 210 changesat least one of a color, a shape, and a size of a point plotted on sucha vector scope image according to the color coincidence degree that canbe determined on the basis of the residual color difference information.As a result, the center area in the vector scope image is colored in acolor corresponding to the residual color difference as shown in FIG. 17.

Moreover, the color-coincidence-information generation unit 210 maygenerate a screen or a message to prompt a user to perform the colormatching again in addition to or in place of the generation of theabove-mentioned various display images that display the residual colordifference. FIG. 18 is a flowchart showing a process for outputting amessage when the residual color difference value is not less than athreshold. The color-coincidence-information generation unit 210 mayexecute the process of FIG. 18 together with the process of FIG. 14 orafter the process of FIG. 14 .

In a step S1901, the color-coincidence-information generation unit 210obtains the maximum residual color difference value from all the pixelsin the color-matched image of the target camera 101. In a step S1902,the color-coincidence-information generation unit 210 determines whetherthe obtained maximum residual color difference value is equal to or morethan its threshold. The threshold may be a residual color differencevalue that is expected to be reduced by regenerating the correction LUT,for example. In the example in FIG. 16 , the threshold of the residualcolor difference value may be 2.0 or more.

When the obtained maximum residual color difference value is not lessthan the threshold, the color-coincidence-information generation unit210 proceeds with the process to a step S1903. When the obtained maximumresidual color difference value is less than the threshold, thecolor-coincidence-information generation unit 210 finishes this process.In the step S1903, the color-coincidence-information generation unit 210generates the screen or message to prompt the user to perform the colormatching again. The color-coincidence-information generation unit 210outputs the generated screen or message to the display unit 211. Thedisplay unit 211 displays the screen or message. After that, thecolor-coincidence-information generation unit 210 finishes this process.Thereby, the color-coincidence-information generation unit 210 cangenerate the screen or message to prompt the user to perform the colormatching again when the maximum residual color difference value that canbe determined on the basis of the residual color difference informationis not less than the threshold.

Although the present invention has been described in detail on the basisof the suitable embodiments, the present invention is not limited tothese specific embodiments, and various configurations that do notdeviate from the scope of the present invention are also included in thepresent invention.

For example, when generating the vector scope image shown in FIG. 17 ,the color-coincidence-information generation unit 210 may change thepoint plotted on the vector scope image in accordance with the RGBvalues of the image from the target camera 101 or the arithmetic valuebased on the RGB values. In addition, for example, when generating thevector scope image, the color-coincidence-information generation unit210 may calculate the residual color difference from the image from thereference camera 100 simultaneously and may plot a different point inaccordance with the residual color difference from the image from thereference camera 100. When such a point is plotted, the user can easilyintuitively discriminate an area where the colors are matched in thevector scope image.

Other Embodiments

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2022-053840, filed Mar. 29, 2022, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A display control apparatus comprising: a memory device that stores a set of instructions; and at least one processor that executes the set of instructions to: obtain an adjustment image from an adjustment image pickup apparatus that performs predetermined color matching with a reference image pickup apparatus; generate residual color difference information showing color difference from a reference image picked up by the reference image pickup apparatus that remains in the adjustment image; and generate display information from the residual color difference information.
 2. The display control apparatus according to claim 1, wherein the predetermined color matching is performed by comparing images obtained by picking up a predetermined object by the adjustment image pickup apparatus and the reference image pickup apparatus.
 3. The display control apparatus according to claim 2, wherein the predetermined object comprises a color chart.
 4. The display control apparatus according to claim 1, further comprising a holding unit configured to hold the reference image used for the predetermined color matching with the adjustment image pickup apparatus, wherein the at least one processor executes instructions in the memory device to generate the residual color difference information corresponding to a color coincidence degree between the images by comparing the adjustment image with the reference image held in the holding unit.
 5. The display control apparatus according to claim 1, wherein the at least one processor executes instructions in the memory device to generate an image in which a color of an area where the residual color difference information is generated in the adjustment image is converted into a color corresponding to a value of the residual color difference information as the display information.
 6. The display control apparatus according to claim 1, wherein the at least one processor executes instructions in the memory device to generate a color distribution image corresponding to the adjustment image as the display information; and display color distribution corresponding to a color coincidence degree that can be determined based on the residual color difference information on the color distribution image.
 7. The display control apparatus according to claim 6, wherein the at least one processor executes instructions in the memory device to generate an image that displays at least one color phase among a plurality of color phases included in the adjustment image as the color distribution image.
 8. The display control apparatus according to claim 1, wherein the at least one processor executes instructions in the memory device to: generate a vector scope image about the adjustment image as the display information; and plot a point of which at least one of a color, a shape, and a size corresponds to a color coincidence degree that can be determined based on the residual color difference information on the vector scope image.
 9. The display control apparatus according to claim 1, wherein the at least one processor executes instructions in the memory device to generate and display at least one of a screen and a message that prompt a user to perform the predetermined color matching again in place of a display image that displays the residual color difference information in a case where a maximum residual color difference value that can be determined based on the residual color difference information is not less than a threshold.
 10. The display control apparatus according to claim 1, wherein the at least one processor executes instructions in the memory device to generate and display at least one of a screen and a message that prompt a user to perform the predetermined color matching in addition to a display image that displays the residual color difference information in a case where a maximum residual color difference value that can be determined based on the residual color difference information is not less than a threshold.
 11. A control method for a display control apparatus, the control method comprising: obtaining an adjustment image from an adjustment image pickup apparatus that performs predetermined color matching with a reference image pickup apparatus; generating residual color difference information showing color difference from a reference image picked up by the reference image pickup apparatus that remains in the adjustment image; and generating display information from the residual color difference information.
 12. A non-transitory computer-readable storage medium storing a control program causing a computer to execute a control method for a display control apparatus, the control method comprising: obtaining an adjustment image from an adjustment image pickup apparatus that performs predetermined color matching with a reference image pickup apparatus; generating residual color difference information showing color difference from a reference image picked up by the reference image pickup apparatus that remains in the adjustment image; and generating display information from the residual color difference information. 